Savion Tolar, 7, left, reaches to grab the foot of 8-month-old Joshua Jarrett-Schell during a Roots of Empathy program last year in Washington. (Sarah L. Voisin/The Washington Post)

Many older Americans may not like — or at least empathize with — Kids These Days. But there are selfish reasons to spend more taxpayer money on the young all the same.

This is the framework I wish Harvard political scientist Robert Putnam had emphasized in his new bestseller, “Our Kids: The American Dream in Crisis.” He intersperses tear-jerking anecdotes with hard-nosed statistics to illustrate how children from poor families today have fewer chances for upward mobility than their counterparts from yesteryear. Poor kids and young adults, he argues, are the innocent victims of a widening “opportunity gap.”

His takeaway is that Americans need to return to a more communitarian view of child rearing. “To ignore these kids violates our deepest religious and moral values,” Putnam writes in his final chapter, in which he advocates devoting more funding to social programs that would shore up opportunities for low-income youth. “America’s poor kids do belong to us and we to them. They are our kids.”

I, too, consider myself a champion of public programs that improve the lives of poor youth. But I’m pessimistic that urging compassion will change the way Americans think about economically immobile youth for two major reasons. Both are related to demographics: The country is getting older, and its younger generations are less white.

These trends are sometimes referred to as the “graying” and the “browning” of the country. Together they portend that, despite Putnam’s urging, voters will actually become less sympathetic to spending on young people over time. We may instead end up systemically underinvesting in an entire generation of Americans.

The fact that the country is aging bodes poorly for public spending on today’s youth. That’s not just because government commitments to the old, such as Medicare and public pensions, threaten to crowd out funds for other programs. It’s also because research suggests that older Americans generally do not support spending on the young. One famous study by MIT economist James Poterba, for example, found that a rise in the share of elderly residents in an area correlated with a significant reduction in per-child educational spending. Disturbingly, Poterba also found that the reduction is especially big when elderly residents and the school-age population are from different racial groups.

This latter finding jibes with other economic and historical research showing that greater ethnic and racial fragmentation, independent of age, is associated with lower rates of social spending on productive public goods such as education and roads, as well as lower support for welfare and income redistribution programs. This pattern has been documented both across the United States and in other developed countries.

Now consider the fact that younger Americans are increasingly likely to be nonwhite — that is, different than most older Americans. About half of children born today are racial or ethnic minorities. As of last fall, America’s public schools were already “majority-minority,” according to government data.

In other words: Old people don’t like to spend money on the young, and voters more broadly are less supportive of social spending when a population becomes more diverse. Layer the “graying” onto the “browning,” and it starts to look unlikely that empathy will pave the way to expanded social spending for young people. The fact that the young look different from the old in ways besides age and ethnicity — including family structures — suggests other barriers to intergenerational empathy, too.

What do you do about this, if you want to generate more support for social programs that help improve opportunities for younger Americans?

One option is to encourage more young people to vote. Part of the reason the so-called gray peril is so perilous to social spending on the young is not only that older people are becoming more numerous but also they’re more politically engaged than their younger counterparts.

The other option is to remind older Americans that when it comes to investing in youth, they have skin in the game, too. Older people need a thriving, full-potential-achieving next generation to pay for their Medicare and Social Security; to care for them in their dotage; to grow the economy and thereby improve their living standards; and, as demographer Dowell Myers has argued, even eventually to buy their homes.

I suspect that this appeal to self-interest, rather than the moral arguments for nurturing the next generation that Putnam emphasizes, will be the key to converting more people to the equity-of- opportunity cause. But compassion is always welcome, too.